Copolymer of styrene and a polyester of endomethylene tetrahydrophthalic acid and a glycol



Patented June 10, 1947 COPOLYMER OF STYRENE AND vA POLY- I ESTER OFENDOMETHYLENE TETRAHY- DROPHTHALIC ACID AND A GLYCOL Howard L. Gerhart,Milwaukee, Wis., assignor to Pittsburgh Plate Glass Company, AlleghenyCounty, Pa., a corporation of Pennsylvania No Drawing. ApplicationDecember 3, 1943, Serial No. 512,7.67

4 Claims.

The present invention relates to synthetic resin compositions and it hasparticular relation 2, acid from maleic anhydride and cyclopentadiene iswritten to the plasticization of resins comprising the H polymerizationproducts of polymerizable oleflnic compounds embracing styrene, vinyliccom- 5 H0 C-C=0 pounds, acrylic acid and its esters and other com- I Ipounds containing reactive olcfinic groups. H C 4 One object of theinvention is to provide olefin polymer resins which are very hard,tough, resistant to solvents and resistant to softening by heat. Thereaction is discussed in greater detail in co- A second object is toprovide a mixture which pending application F 470,023, med Decemwillundergo conjoint polymerization of a ber 24, 1942, and ent1tled,Preparation of tetraparative1yrapidrate hydrophthalic anhydrides, HowardL. Gerhart Resins have, therefore, been prepared by the and LeonAdamspolymerization through the addition reaction of In the Presentapplication the term 15 reactive unsaturated groups in oleflnic comt0 beconstrued not only as including the free pounds Styrene is a spe ifiexample f such acids, but, also, the anhydrides of ciscap-unsatucompounds However others including vinyl rated,a,p-dicarboxylic acids, which interchangeacetate, vinyl chloride,acrylic acid, methacrylic ably can undergo estelmcation Wlth dihydroxyacid and esters g" methyl and ethyl esters) of alcohols to form theesters contemplated herein. acrylic acid and methacrylic acid can bepoly- Chlommaleic a anhydride can also be merized in a similar manner. vp y The styrene polymer is inherently brittle and The acids 0 anhydrideswill react with yis, also, subject to thermal softening at fairly dmxy310011015. Such as yco diethylene ycol, low temperatures. It has,heretofore, been protriethylene ly rim thylene gly tetraposed to improvethese properties by incorporatethyene glycol 01' the like 120 form esterchains ing inert or non-reactive plasticizers such as Such i dimethylphthalate therein. In some instances, the product is thus improved, butstill it is not 2% 3:? entirely satisfactory.

In accordance with the provisions of the present invention, it isproposed to plasticize adden- -g%- -g-g- 2 2 dum resins and such asthose resulting from the A (L polymerization of styrene, with a reactiveplasticizer such as the dihydroxy alcohol esters of o t t y p tha i d ad yc or tetrahydrophthalic acid or the homologues of tetrahydrophthalicacid. 3

The tetrahydrophthalic acid and the homologues thereof contemplatedherein are easily 40 HCOH OH prepared by subjecting maleic acidanhydride or mil-(P00041320H10-C-GC-C-0CHICK: its homologues toaDiels-Alder type reaction with i H H i, 3 H H 8 a conjugate diolefinsuch as butadiene, cyclopentadiene, or cyclohexadiene. Theaformula offrom endo y e t t a ydrop t a ic acid the anhydride oftetrahydrophthalic acid from and y maleic acid anhydride and butadieneis written It is to be observed that the cyclic residues of the acidmolecule in the ester linkage each ino clude an olefin linkage or doublebond. The potential reactivity of this double bond is very high eventhough it is in a cyclic structure and is remote from the carboxyls, sothat when H0 the polyester is heated during the last stages of H theesteriflcation when the acid number ap- HI I preaches 10, the molecularchains cross link and that of endomethylene tetrahydrophthalic throughthe double bonds to form a three dimensional polymer which is veryinsoluble. Likewise a soluble polymer having an acid number of 40 orless will absorb oxygen at the double bonds and be converted to apartially oxidized resin which may easily become insoluble. Thus, it isseen that the double bond will very easily engage in polymerizationreactions. Therefore, it is desirable to discontinue esterifieationbefore the gel stage is reached. Also, an inert atmosphere should bemaintained over the reactants and the resultant ester to preventpolymerization by oxidation.

Esters can be made with many common polyhydroxyl compounds but theesters which are most useful are those having two hydroxyl groups suchas ethylene glycol, diethylene glycol, triethylene glycol, trimethyleneglycol, etc. A very small amount of glycerine may be used to replace aportion of the glycol in the preparation of these esters. The glycerinetends to make the polyesters less soluble. The most desirable esters arethose having an acid value of 40 or less, preferably below about 30 butnot so low as to be gelled or partially gelled. These esters areprepared in the presence of an inert gas totally free of oxygen and theymay be prepared by a method which involves the use of a solvent tofacilitate the removal of the water. The procedure follows the generalmethods well known in the preparation of the polyester type resins. Thefollowing examples are illustrative of such methods:

Example A A mixture of 164 parts of endomethylene tetrahydrophthalicanhydride and 116 parts diethylene'glycol is heated as rapidly as isconvenient to 180 C. under air reflux condensation. The temperature israised gradually to 220 C. while a rapid stream of inert gas is passedthrough the liquid. The water formed in the esterification process isthus carried out of the reactor as rapidly as it is formed. Heating iscontinued at 220 C. until the liquid ester has an acid number of 40 orless. The ester is then cooled and stored in an inert atmosphere.

The reaction may also be conducted in a solvent substantially asfollows:

Example B Charge 146 parts tetrahydrophthalic anhydrlde, 116 partsdiethylene glycol, and 20 parts xylol into a container equipped with aside arm take-off. Heat the mixture to boil off the xylol and waterrapidly. Separate the water from the xylol and return the xylol to thecontainer substantially as rapidly as it distills. Continue therefluxing until the acid number of the ester is less than 40. Pass arapid stream of inert gas through the liquid so as to free the finishedester of most of the boiling xylol. Remove last traces of xylol atreduced pressure again in an inert atmosphere.

In the examples, the proportions are by weight.

It has been found that while the esters are plasticizers for styreneresins and similar resins formed by addendum polymerization ofpolymerizable olefins, they are also reactive with the olefin or itspartial polymer and form true reaction products from which the resincannot be extracted by mere physical methods. Heretofore, the resinprepared from styrene was very brittle in the unplasticized form. It wasalso a thermoplastic resin which softened when it was heated to 100 C.When this resin, however, is prepared in the presence of an ester ofthis type, the resin is set resin.

The following compositions illustrate the types of mixtures which can bepolymerized to resins by this contemplated method:

EXAMPLE I Composition Conditions Description el Plastic 10 partsStyrene.. 10 parts Dicthylcne glycol ester of endomethylenetetrahydrophthalic acidv part llcnzoyl perox- 18".".

[00 C. for l hourv J'iinrd, transparent L resin.

EXAMPLE II Composition Conditions Description or Plastic 20 partsStyrene 8 parts Same ester as in (I). .03 part Benzoyi peroxide.

} C. for 15 hours Very hard resin.

EXAMPLE III Composition Conditions Description of Plastic 27.5 partsSame ester as in s arl'st'ir'rljIIIIllI .03 part Benzoy] peroxide.

100 C. for 5 hours.

Soft and gummy, low tensile strength.

EXAMPLE IV Composition Conditions Description of Plastic 18 partsStyrene 6 parts Same ester as in (I).

}l00 C. for 5 hours.

Very hard resin.

EXAMPLE V Composition Conditions Description of Plastic 20 parts Styrene5 parts Triethylene glycol ester of endomcthylcne tetrahydrophthalicanhydride .03 part Benzoyl peroxide.

10 hours 60 0..

{Very hard, clear transparent.

EXAMPLE VI Composition Conditions Description of Plastic 20 partsStyrene 5 parts Tetraethylene glycol ester of endomethylenetetrahydrophthalic anhydride .03 part Benzoy] peroxide.

10 hours 60 C.

{Excellent hardness and clarity.

XAMPLE VII Composition Conditions Description of Plastic 12 partsStyrene 20 parts Diethylene glycol ester of tetrahydrophthalicanhydride.

10 hours 60 0..

Very hard resin.

Exam VIII Composition Conditions gi gg g 35 parts Styrene partsDiethylene glycol ester of tetrahydro- 15 hours 110 0. Very hard resin.phtbalic acid 0.4 part Benzoyl peroxide.

EXAMPLE 1 Composition Conditions ggg g g 1m parts Dieth ylene glycolester of tetrahydro- Tough plastic havphthalic acid 5 hours 60 0... inggood impact 450 parts Styrene strength. 3.4 parts Benroyl peroxide.

During the mixing operation, rapid agitation is desirable to preventpremature gellation of the resin.

Catalysts such as benzoyl peroxide can be employed but are not essentialto the reaction.

In the foregoing examples, styrene may be substituted in whole or inpart by other polymerizable oleflns such as methyl, methacrylic acidester. vinyl acetate, and others that similarly polymerize.

The ratio of ester to polymerizable olefin may be varied over a broadrange to provide products having properties especially suited forparticular conditions. For example, styrene may constitute from 1 to 99percent of the mixture dependent .upon the characteristics desired inthe product.

A ratio of 50 percent is very satisfactory for most purposes.

The temperature of polymerization can be as low as substantially normalroom temperature. Higher temperatures increase the rate of reaction butshould be adjusted to obviate undue violence. Also, it should not be sohigh as to induce decomposition or charring of the reactants of thereaction product.

The preparation of a laminated product from the resin is illustrated bythe following example:

EXAMPLE Two glass plates were coated on one side with bath soap. Thesoap was rubbed off lightly and the glass plates buffed with a muslinwheel. Four strips of cotton duck cloth were soaked with the aboveingredients, e. g., from ExampleI (which were easily dissolved on thesteam bath) and placed between the prepared glassplates. The assemblywas placed in an-oven at 60 C. for

(three hours. After cooling, the glass plates agitation is necessary toprevent gellation even though the temperature be kept below 65 C.

2. The intimately mixed composition can be.

Instead of-the soap, a thin film ofset to a gel or jelly within 5 to 60minutes by (a) heating to 60 C. or (b) by irradiating in direct sunlightat 30 C.

3. The gelled resin will polymerize rapidly at 60 C. and above too. hardplastic body which generally shrinks from the casting vessel. Aconvenient heating schedule after complete gellation is one hour at 100C.

4. At temperatures above 130 C., the hardening process is very rapid.Very hard thin castings have been prepared by heating the gelled resinto 130 C. for 8 minutes.

5. Fibrous materials have been laminated at pressures slightly aboveatmospheric by heating cloth, paper and Fiberglas soaked with thefreshly mixed compositions. The process is ideally suited for laminatingat low pressures, since no complicated pressure developing mechanism isnecessary. Thus, the sheets may be placed between two glass plates andthe assembly heated several hours at 60-100 C. Likewise, the morecomplicated shapes may be formed within or around a pattern while heatand pressure is applied by inserting them in the well-known vacuum bag"and subjecting the bag to pressure of a hot inert liquid.

Description of resins Resins prepared from the above compositions arecharacterized by extreme surface penetration hardness. When the rawmaterials are in the highest state of purity, the finished resins may beperfectly transparent. The clarity may vary from hazy translucency tofull transparency depending upon the method of polymerization. It isgenerally observed that resins prepared at a higher temperature such asat 100 C. are more transparent than resins prepared at room temperature.

It will be appreciated that the schedules given are more than sufllcientto produce complete polymerization. Usually some additional heating cando no harm. It will, also be appreciated. that light is a very effectivecatalyst and that the heating schedule is shortened materially in strongsunlight or irradiation of a similar na- The embodiments of theinvention herein shown and described are to be considered merely asbeing by way of example. It will be apparent to those skilled in the artthat numerous modifications may be made therein without departure fromthe spirit of the invention or the scope of the appended claims. i

What I claim is:

1. A method of preparing a hard, resinous copolymer product whichcomprises heating a mixture composed 01 50 to of styrene and 20 to 50%of an ester of endomethylene tetrahydrophthalic acid and a glycolconsisting of 2 to 4 ethylene groups between the hydroxyls, the ethylenegroups being bridged together by ether-ongen linkages, the heatingoperation being effected at a temperature of 60 to 100 C. and in thepresence of a peroxide type catalyst and being continued until said hardtough resinous copolymer product is obtained.

2. A method of preparin a hard, tough, resinous copolymer product whichcomprises heating to a temperature of 60 to 110 C. a mixture consistingof 20 to 50% of polyesters of diethylene glycol and endomethylenetetrahydrophthalic acid and the rest styrene, the heating operationbeing continued until said product is formed.

3. As a new product a hard resinous body consisting of the copolymer of50 to 80% of styrene and 20 to 50% of a polyester of endomethylene'tetrahydrophthalic acid and a glycol containing 2 to 4 ethylene groupslinked together by oxygenether linkages.

4. As a new product a. hard tough resin body consisting of a copolymerof 50 to 80% of styrene and 20 to 50% of a polyester of endomethylenetetrahydrophthalic acid and diethylene glycol.

HOWARD L. GERHART.

REFERENCES CITED The following references are of record in the file ofthis patent:

8 UNITED STATES PATENTS Number Name Date 1,860,730 Brooks May 31, 19422,195,362 Ellis (1) Mar. 26, 1940 2,235,447 Bradley et a1 Mar. 18, 19412,251,297 Soday Aug. 5, 1941 2,255,313 Ellis (2) Sept. 9, 1941 2,311,260Staif Feb. 16, 1943 2,31 ,780 Pellett May 25 1943 2,319,826 Pellett (2)May 25, 1943 2,359,038 Hop! (2) Sept. 26, 1944 2,351,019 Gerhart Oct.24, 1944 2,369,689 Robie Feb. 20, 1945 FOREIGN PATENTS Number CountryDate 598,732 Germany June 26, 1930 695,756 Germany Aug. 1, 1940 OTHERREFERENCES Hackhs Chemical Dictionary Blakiston 1937, (2nd ed.), page652, article olefine. (Copy in Division 50.)

Kropa Ind. & Eng. Chem., Dec. 1939, pp. 1512 (Copy in Scien. Libr.260-42.)

Mattiello, Protective 8; Decorative Coatings, 1941, Vol. I, pages 423 to425. (Copy in Div. 50.)

